Live attenuated influenza vaccine (LAIV) is a type of influenza vaccine in the form of a nasal spray. It is an attenuated vaccine, unlike most influenza vaccines, which are inactivated vaccines. LAIV is administered intranasally, while inactivated vaccines are administered by intramuscular injection. Both live attenuated and inactivated vaccines are typically trivalent, since they contain material from three different influenza virus. LAIV is sold under the trade name FluMist in the United States and Canada. (source)